Field of the Invention
The present invention relates to an apparatus and a method for processing a front-side surface and/or a backside surface of a substrate, such as a wafer, which requires high cleanliness.
Description of the Related Art
In recent years, various devices including memory circuits, logic circuits, and image sensors (e.g., complimentary metal-oxide-semiconductor (CMOS) sensors) have become more and more highly integrated. In the processes of fabricating these devices, foreign substances, such as fine particles and dusts, may be attached to the devices. The foreign substances attached to the devices could be a cause of a short circuit between interconnects and a malfunction of the circuit. Therefore, in order to increase reliability of the devices, it is necessary to clean a wafer on which the devices are fabricated so as to remove the foreign substances from the wafer.
The foreign substances, such as fine particles and dusts, may also be attached to a backside surface of the wafer, i.e., a bare silicon surface. The foreign substances on the backside surface of the wafer may cause the wafer to be separated from a stage reference surface of an exposure apparatus and/or may cause the wafer surface to tilt with respect to the stage reference surface, resulting in a patterning shift or a focal length error. In order to prevent such problems, it is necessary to remove the foreign substances from the backside surface of the wafer as well.
There has recently been developed a patterning apparatus based on nanoimprint technology, rather than the optical exposure technology. In this nanoimprint technology, a mold, which has predefined interconnect patterns, is pressed against a resin material formed on a wafer to transfer the interconnect patterns to the resin material. In such nanoimprint technology, it is required to remove the foreign substances existing on the surface of the wafer in order to avoid transfer of unwanted spots between the mold and the wafer and also between wafers.
It has been customary to scrub the wafer with a pen-shaped brush or a roll sponge while rotating the wafer. However, such a cleaning technique has a low capability of removing the foreign substances. In particular, it is difficult for the conventional cleaning technique to remove the foreign substances having a size of 100 nm or more.